The present invention relates to a CNC (computer numerical control) lathe and relates more particularly to such a CNC lathe having a secondary tool turret for processing the rear end with pick off from main spindle by counter spindle workpiece delivered through a tailstock feed mechanism.
A CNC lathe is a computerized cutting metal-working machine having a computer numerical control panel for giving instructions to a central processing unit in controlling the operation of a variety of mechanisms to process a metal workpiece. By means of the control of the central processing unit, the working efficiency and the capacity of the lathe are greatly improved. FIG. 1 illustrates an automatic lathe according to the prior state of the art. This structure of the lathe includes a work spindle mounted in the head stock on a bed thereof at bed thereof at one side and controlled to grip and rotate the workpiece, a rotary cutting tool carrier having a feed chuck and a set of cutting tools controlled to process the front end of the workpiece, and a set of radial processing mechanisms arranged around the work spindle and controlled to process the outer diameter of the workpiece. This automatic lathe can only process the outer diameter and the front end of the workpiece. Once the front end and the outer diameter of the workpiece have been processed, the workpiece is cut off and carried away. For making a bore or bolt hole on the rear end of the workpiece, the workpiece should be separately processed. Another disadvantage of this type of automatic lathe is that the work spindle can only feed an elongated metal rod out to position for processing, and therefore it is not suitable for processing a short metal workpiece. FIG. 2 illustrates another variety of CNC lathe according to the state of prior art. This variety of CNC lathe includes a main tool turret for processing the front end of the workpiece, a set of radial processing mechanisms for processing the outer diameter of the workpiece, and a tailstock tool holder supported on a horizontal slide to hold two tools for processing the rear end of the workpiece. This type of CNC lathe is still not satisfactory in performance. Because the tailstock tool holder can only carry two cutting tools, the cutting tools may have to be frequently changed according to different working requirements. Frequently changing the cutting tools greatly affect the processing speed and efficiency. Furthermore, this variety of CNC lathe has no automatic feed mechanism for feeding short metal workpiece. If a short metal workpiece is to be processed, it must be carried into position by a robot. However, the use of a robot greatly increases the installation space and cost of the lathe and complicates the maintenance work.